Process for purifying the nitrogen-hydrogen mixture in the synthesis of



March 14, Q JONES Y.

v PROCESS FOR PURIFYING THE NITROGEN-HYDROGEN MIXTURE IN THE SYNTHESISOF AMMONIA Original Filed April 2, 1927 Resina Mar; 14, 1933 Railsyst-UNITED STATES PATENT oli-Fics Louis c. JONES, or' GREENWIGII,coNNEcrIcur, AssIeNoR 'ro :ENGINEERING cosPonATIoN, or NEW Yoax, N.' Y.,A. coRroRx'rIoN or nnnawann i raocnss ron. rUmYINe THE NITROGEN-HYDRQGENIux'rurtn IN rma: SYNTHESIS or AMMONIA OriginaI No. 1,794,903, datedMarch 3, 1931, Serial 110.180,61?, led Api-i1 2, 1927. Application for`reissue led Hay 17, 1932.

My invention relates* generally to the synthetic manufacture of ammoniafrom its elcments and is particularly adapted to improved processes forpurifying the gaseous mixture of hydrogen and nitrogen in themanufacture of anhydrous ammonia.

After compressing mixtures of nitrogen 'and hydrogen in combiningproportions 1n theprocess of making synthetic ammonia, the gas mixturestill contains, in addition to other impurities, certain amounts ofmoisture in equilibrium at the pressure and temerature involved. Thismoisture acts in- ]nriously upon the ammonia catalyst and when anhydrousammonia is produced causes contamination of product.

At pressures above 100 atmospheres, the amount of this moisture isnecessarily small,

but it is considered important to remove it which has been done brefrigeration, washin with liquid anhy rqus ammonia, `or by ot er means.

The make-up as mixture is usually freed as far as possibe from carbondioxide-by washing in caustic soda or otherwise since this, too, is aninjurious impurity.

, In industrial practice, therefore, it is extremely advantageous insecuring satisfactory yields to remove, if possible, even the lasttraces lofwthese harmfulyimpurities from the nitrogen-hydrogen mixturebefore treating same catalytically.

I have found that both these impurities and also others, such as oilparticles and dust, can be eectively removed in the solid form 21m,+co2+n2o= (Nimmo,

The amount of moisture concerned in this reaction is necessarily small,since gas at 100 atmospheres pressure, saturatedl with water vapor at 20C.,"contains (by volume) only about 1 Apartof moisture to 30,000 partsof serial No. 611,929.

gas. -Therefore, the same amount of carbon dioxide is required to removethis water lwith the formation of ammoniumscarbonate.

Ordinarily, unless this carbon dioxide is completely removed, the solidammonium carbonate formed will ultimately cause diiii- 'cult by stoppageinthe system of piping.

o wever my process, an enlargementlin the circulating system causinginterruption of the gas current and., containing surface-` givingmaterial may advantageously utiized to provide for the solid materialsdeposited.

In actual practice, -haye found that the r deposition of this solidmatter brings down with 1t any other solid or .liquid impurities presentin the gas current such as particles of oil and dust, all of which arethereaftervre" moved.

M improved process is carried out in 'pract1ce y bringing thecarbon'dioxide containmg gas into the circulating system containing thegasmixture for. use in the synthesis of ammonia immediately 'precedingor directly into an enlargement 1n the circulation system aftercompression but before catalysis. This enlargement may consist of anysuitable chamber Vfilled with Raschig'Ik rings or similarjbailling orfiltering material which will cause the deposit'of the solid or diquidimpurities without stoppage ofthe as current which is thereby freed fromsu injurious substances.V Two such enlargements arranged inparallel-will advantageously permit convenient of one while the otherremains in operation.

The essential features of Vmy' process, thcrefore, involve theintroduction ofsmall but controlled amounts of carbon dioxide into thegases under pressre in order to produce a solid compound containingmoisture which compound also removes the carbon dioxide introduced aswell as other solid and liquid impurities such as oil and dustparticles, such impurities in solid form being yremovefdffrom the gasesin circulation before production ofA ammonia. The amount of carbondioxide should not exceed one-half by volume the ammonia in the gases incirculation.

The single figure in the drawing reprcnts diagrammatically a layout ofthe various elements of the apparatus used in carrying out the' process.

In this figure the make-up gases indicated at 1 and including nitrogen,hydrogen, car'- bon dioxide and water vapor pass to the com-y pressor 2Where they are put under suitable pressure. After compression the.residual ammonia 3 remaining 1in the .catalyst ases after the ammoniaremoval 4 is intro ucedI into the line,I and this admixture of gasesthen goes to the enlarged chamber 5. In this enlarged chamber theresidual ammonia, the carbon dioxide and the water combine to form solidammoniumV carbonate which is precipitated as such therein. Thisprecipita- -tion carries with it anC oil, dust, or the like which mayoccur in t e gases at this point and thesolid and liquid impurities thusremoved may be removed from the chamber in any suitable-manner, From thechamber 5 the gases pass to the ammonia catalyst apparatus 6 where theconversion of the nitrogen and hydrogenI into ammonia takes. place. Themajor. portion ofthe resultant ammonia is removed as at 4, the residualammonia .3

going back into kthe cycle as indicated.

As an'alternative method, where the ori inal make-up gases eithercontain no or o y decientquantities of carbon dioxide which arenotenough to combine with the carbon dioxide and water to Vform ammonium'carbonate, additional quantities of carbon dioxide 7 may be introducedeither before orafter compression as indicated. In this way there arealways lsuiilicient quantities of the neces,- sary ingredients orimpurities to cause a combination thereof and precipitation as ammoniumcarbonate with effective removal' of these impurities. i

I claim: v '4 l 1. In a process of synthetically producing ammonia, inwhichI a mixture of hydrogen j andnitrogen `is passed over a catalystand a portion o the ammonia is removed by condensation 'or the like, theimprovement which up gas containin portion of thev ammoniais removl.compr-'isos admix'ing the circulat' y gas containing residual ammoniawith e makecarbon dioxide in laA regionof reduced ve ocity anddepositing solid ammonium carbonate formed by the resultingreaction insaid region. h p 2; In a process of synthetically producing ammonia, inwhich a mixture of 4hydrogen and nitrogen is passed over a catal andda,`

by con;-

u densationor the like, the improvementwhich comprises contacting thecirculating anims 'thsi's-ofmmonig-bymn- Y fence tion of a gas mixtureincluding hydro n and'nitrogen cyclically over a catalyst, t en throughlan ammonia separator, then over the catalyst and so on, 'theimprovement which comprises supplyin make-up gases contaminated with'carbon culating gas mixture leaving the ammonia separator, andseparatingammonium carbonate/formed from theesulting gas mixture as asolid before the remaining. gas mixture is passed over the catalyst. i

4. In a process of synthetically producing ammonia by cyclicallycirculating a mixture of hydrogen and nitrogenover acatalyst andremoving a portion of the ammonia formed thereby by condensation or thelike, the improvement in purifying the mixture which comprisescontacting the circulating mixture containing residual ammonia withmakeup gases containing impurities, reacting impuritiest of the make-upgases with the residual ammonia in vapor phase to form solid compoundsin a region of reduced velocity and baflled flow, and separating thesolid compounds before the circulatingl gas mixoxide to the cirture ispassed over the? catalyst and before gaseous. taining residual. ammoniawlth ,the make-y

